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Abstract

We investigate the fine structure of the optical spectrum of a broad-area laser diode with approximately 30-MHz resolution using spatially-resolved self-heterodyning technique. We show that this method is capable of measuring the relative powers and spacings of the individual lateral modes.

Figures (6)

Simulated pictures of spatially-resolved RF spectra of a BALD (near field). Left: Spatial profiles of RF power corresponding to mode beating frequencies. The vertical axis of the graph has both RF frequency and intensity meanings. Number of shown lateral modes is P = 5. The corresponding number of the resulting beat frequencies is P(P–1)/2 = 10. Right: Same as picture on the left, but with intensity shown by color scale (i.e., vertical scale represents RF frequency only). The double-script notation of each plot indicates the corresponding indices of the lateral modes contributing to the given RF component.

Simulated picture of angularly-resolved RF spectra of a BALD (far field). Left: Spatial profiles of RF power corresponding to mode beating frequencies. The vertical axis of the graph has both RF frequency and intensity meanings. Number of shown lateral modes P is 5. The corresponding number of resulting strong beat frequencies is P–1 = 4 (shown in the bottom half of the picture). Right: Same as picture on the left, but with intensity shown by color scale (i.e., vertical scale represents RF frequency only). The double-script notation of each plot indicates the corresponding indices of the lateral modes contributing to the given RF component.